A sodium-sulphur cell has a solid electrolyte, usually of beta-alumina, which separates molten sodium forming the anode from a cathodic reactant; the cathodic reactant comprises essentially liquid sulphur together with polysulphides of sodium produced by the passage of sodium ions through the electrolyte into the cathodic reactant material. The liquid sodium is a good electrical conductor and there is thus little problem in effecting electrical contact to the sodium which constitutes one of the electrodes of the cell. The cathodic reactant however is a poor electronic conductor as well as being highly reactive chemically. It is necessary therefore to provide, in the liquid reactant material, an electronic conductor. This has to be porous to permit of free access of the cathodic reactant material to the neighbourhood of the electrolyte. Electrically, this conductor forms the path or part of the path from a cathode current collector for the electrical charge given up by the sodium ions which pass through the electrolyte and combine with the sulphur in cathodic reactant material. It is the usual practice to employ carbon or graphite felt as the porous electronic conductor in the cathodic reactant. Carbon or graphite is used in order to withstand the corrosive conditions of the molten cathodic reactant. The material is typically composed of carbon fibres about 10 microns diameter in a loosely packed assembly with an overall density of about 0.1 g cm.sup.-3 which represents a porosity of approximately 95%. The felt material provides adequate surface area for the electrochemical reaction to take place but the pore structure is not favourable for the flow of the liquid reactant material within the electrode. The fibres in the material are not rigidly interconnected and felt can be compressed in one direction to about half its natural thickness without damage. This property is advantageous in that, in a cell having electrolyte in the form of a tube with an annular cathodic region, the felt can be compressed into the annular space in such a way that pressure is maintained between the felt and the current collector; this effects a low contact resistance between the felt and current collector. However this fibre structure has the disadvantage that fibre to fibre contact is poor and may vary during some operations. Thus during continued operation of a cell, both the electrical characteristics and pore structure of the electrode may deteriorate.